The purpose of this contract is to validate previous observations of muscular hypertrophy and hyperplasia in small pulmonary arteries in infants dying of the Sudden Infant Death Dyndrome. If this pathological finding can be documented in a statistically significiant and demographically compatible population this finding may serve to soldiify the hypothesis that recurrent alveolar hypoxemia is the cause of the Sudden Infant Death Syndrome. Furthemore, additional pathological indications of hypoximia are to be sought in this same population. Should these findings be consistently found in SIDS babies, an approach to prevention could be pursued based on prevention of alveolar hypoxemia.